Technical Abstract:
Introduction
Allelochemicals that modify arthropod host-seeking behavior consist of kairomones and allomones. Kairomones are chemical cues that are used for host finding and are thought to play a large role in this process. Allomones consist of attraction-inhibitors and other repellents that interfere with the host-location process. The release of allelochemicals in the field is normally accomplished by using surveillance traps baited with attractant lures, or appropriate candles or aerosol-dispensing devices to release repellents. The downfield distribution of these compounds in the field and subsequent detection by arthropods is not well understood. Therefore, the use of high-field asymmetric waveform ion mobility spectrometry (FAIMS) and ion mobility spectrometry (IMS) to characterize the distribution of these plumes in the field is being explored.
Method
Preliminary work has been directed at acquiring baseline data by studying three compounds under controlled situations. Two repellents were chosen, N,N-diethyl-3-methylbenzamide (DEET) because it is a common topical repellent, and 3,7-dimethylocta-1,6-dien-3-ol (linalool), because it is an attraction-inhibitor that exhibits spatial repellency in mosquitoes. In addition to these two, 1-octen-3-ol, a common commercial surveillance trap attractant, was also examined. Each compound was dissolved in methanol and the headspace of each solution was analyzed by atmospheric pressure chemical ionization/mass spectrometry (APCI/MS). The solutions were then analyzed by APCI/FAIMS/MS on a LCQ ion trap system (ThermoFinnigan). Methanolic solutions of these three compounds were also analyzed using a handheld portable IMS (GE Ion Track).
Preliminary Data
The potential of FAIMS and the handheld IMS as portable instruments for field use in the characterization of allelochemical odor plumes is being evaluated. The results from initial studies with APCI/FAIMS/MS show promise for FAIMS to be used as a portable instrument that is amenable to the downstream monitoring of the dispersion from targeted compounds from released sources, such as mosquito traps or vapor-releasing dispensers. Standard solutions of DEET, linalool, and 1-octen-3-ol were used in initial studies to determine the optimum parameters for ion transmission. The optimum compensation voltage (CV) at which each ion passed through the FAIMS cell was obtained by scanning the CV. Calibration studies were conducted using the headspace above methanolic solutions of each of the compounds. From the calibration curves, the sensitivity of the APCI-FAIMS-MS was estimated, and results were compared to those obtained using the handheld IMS device.
Novel Aspect
First application and evaluation of IMS and FAIMS as portable systems to characterize allelochemical odor plumes in the field.